I would think that SSBC would have that bracket, but if you need to find another avenue, I would try Ames, Classic or any of the major 1st gen parts vendors.
And or, try to find something locally, maybe an original from a recycling/junk yard?
Just a few ideas?
You may want to check the FAQ section, (or searc some of the posted topics here) as I believe there has been some talk on this conversion, and if I remember right, some were not so impressed with the system? So before you get too much further... maybe look into that aspect of it all?